Deputy Attorney General Rod Rosenstein was probably “set up” by the White House to justify FBI director James Comey’s firing, according to the second-ranking Senate Democrat likely to question him during a Thursday briefing on Capitol Hill.

It could be the next flash point in a Russia controversy enveloping the Trump administration.

In an interview with USA TODAY, Sen. Dick Durbin, D-Ill., who also sits on the Judiciary Committee, said one of his primary questions for Rosenstein is whether he was instructed by someone at the White House to craft a memo recommending the dismissal of Comey. Rosenstein will appear before a closed-session all-senators briefing.

“The man started a blank slate in this whole thing and then reached a point where he was recommending dismissing Comey and raising a question about whether the investigation should go forward,” said Durbin.

“To every outward appearance he was set up. He devised a memo with a rationale for firing Comey that was laughable politically but he must have believed to be credible from a legal viewpoint,” said Durbin. The White House did not immediately reply to a request for comment. On who gave Rosenstein the orders: “I would guess the president would never do that, someone less might do it for the president, and I don’t know who that is,” said Durbin.

Sen. Richard Blumenthal, D-Conn., who also serves on the Judiciary Committee, echoed Durbin in saying Rosenstein "was really unfortunately used and his reputation exploited."

"It would be interesting to know Rosenstein's contacts in Justice at higher levels and at the White House," said Durbin, who is urging Rosenstein "to maintain your credibility."

Durbin also pointed to the fact that, during an initial hearing before the Judiciary Committee on March 7, Rosenstein wasn’t even aware of some basic facts regarding several U.S. intelligence agencies that concluded Russia had conspired to influence the U.S. election. “He said, ‘I really don’t know anything about that,” said Durbin. “I kind of put him on the spot and said, ‘read it.’ So he did, and he got back to me” with an acceptable answer, said Durbin.

Rosenstein’s memo outlined a series of reasons why Comey should be fired, relying heavily on his conduct during the investigation into Hillary Clinton’s private email server. Trump officials initially said Comey’s dismissal was based on the memo. Trump later told NBC he was thinking of “this Russia thing” when he made the decision to fire Comey.